in india, investigators in mumbai searched for clues in wednesday's triple bombing that killed 17 people and wounded 130 more. others demanded answers to how the city was attacked again, despite stepped-up security. we have a report narrated by john sparks of "independent television news." >> reporter: there was no warning. placed in the streets of mumbai the aftermath of one blast, a few hours later detectives began their investigation. a series of bombs detonated in rapid succession. this not the work of suicide bombers said the police. these were sophisticated devices triggered by timers. these the first attacks here since gunmen from pakistan laid siege to the city in 2008. the authorities were taken by surprise. nobody has claimed responsibility for the attacks, although security experts say a domestic group-- the indian mughadeen are prime suspects. few here can see the point of it. "what do we tell our children," said this man. "they think these adults are mad." why kill innocent people? tonight, security has been ramped up across the nation and the police now better trained and r